Imaging & Tissue Pathology: Core B: This program project focuses on the role of various hepatic antigenpresenting cells, i.e. dendritic, Kupffer and stellate cells, as mediators of hepatic injury and regulators of transplant outcome. The central strength of the proposal lies in the combined experience of the group in the study of liver immunobiology in the context of injury, and each project has a strong immunobiology focus. The projects range from studies of immunity and tolerance to understanding the basic mechanisms behind, and the regulation of, hepatic inflammation resulting from various insults, such as ischemia/reperfusion, sepsis and transplantation. The faculty and staff of the Imaging and Tissue Pathology Core B have had a long term and extensive collaborative publication record with the leaders of each project, both using conventional and advanced imaging techniques. The Core service combines two aspects of optical imaging. Diagnostic and Research Pathology, to be performed by Dr. Demetris, and Fluorescence, Ultrastructural and Advanced Imaging, directed by Drs. Stolz and Watkins and carried out in the The Research Histology Facility and Center for Biologic Imaging, respectively. Together, these two interactive and integrative, but separate, non-overlapping imaging-based facilities are absolutely essential to the research goals of collaborating PLs in this P01 application. The Core is equipped to perform a continuum of optical methods including all types of light, fluorescence, live cell and electron microscopy essential to this program project. The specific aims of the core will be various. We will characterize cellular phenotypes within the liver, we will study cell subtypes and their interactions within living systems, we will perform very high resolution studies of cell structure, phenotype and interaction. We will perform histopathologic investigations of tissue samples from all sources, and also measure apoptosis and necrosis in various model systems. Furthermore, our considerable experience in computerized image processing and morphometry will allow quantitative analysis of observed phenomena to corroborate earlier, possibly quite subtle qualitative changes. This core will be used extensively by all projects, though the imaging tools used will vary from project to project.